The investigators hypothesize that the cellular responses to local and distant production of TGF-b are set by the expression of specific receptors for the cytokine. Aim 1 is to determine the temporal and spatial expression of rat lung TGFR during ontogeny. Aim 2 is to correlate the expression of rat lung TGFR during development with their expression during the repair of perinatal lung injury. Aim 3 is to test whether TGFRI or TGFRII controls production of ECM components by expressing mutated TGFRI and TGFRII in fibroblasts cultured from lungs of fetal rats. Aim 4 is to test the role of fibroblast TGFR expression as instruction for lung development.